The present invention relates to a method and apparatus for adjusting a position at which a waveform is displayed on a waveform display device such as a cathode ray tube (CRT) and a liquid crystal display (LCD) device.
Conventionally, in a waveform display device such as a waveform monitor for displaying a waveform of a video signal, scales are provided, for example, on the vertical axis and horizontal axis on a screen of the display device, i.e., a two-dimensional waveform display area, such that an amplitude, time and the like of the displayed waveform are observed based on the scales. Such a monitor is provided with a vertical (V) position adjustor knob and a horizontal (H) position adjustor knob for observing a waveform, moving a displayed waveform on the screen, or adjusting the position thereof. These position adjustor knobs include, for example, rotary encoders, and move a displayed waveform on the screen by distances corresponding to angles over which the knobs are rotated to adjust the position at which the waveform is displayed.
However, when a displayed waveform is, for example, enlarged, the displayed position may be varied vertically and horizontally with the position adjustor knobs to place the waveform at a position at which an operator can readily view an arbitrary portion of the waveform. In such a case, the operator often experiences difficulties in fine position adjustments when the enlarged display is released to return the waveform to the reference position. More specifically, the resolution of the position adjustment by the adjustor knobs is set high to permit fine adjustments, so that the knobs must be rotated over large angles to move a waveform over a long distance to accurately place the waveform at a relatively remote target position. Moreover, fine adjustments are required near the target position to accurately place the waveform at the target position. Thus, the positioning of a displayed waveform is time-consuming and laborious, and may involve a problem from the viewpoint of rapid measurement.
In this regard, a conventional waveform monitor can reset a position at which a waveform is displayed in the vertical direction. This monitor, however, forces an operator to select a menu and again select a reset function from the menu for resetting a displayed waveform to a reference state in which a zero point on the waveform matches a zero point on the scale on the vertical axis.